Adhesion promotion in printed circuit boards

ABSTRACT

An adhesion promotion process and composition for enhancing adhesion between a copper conducting layer and a dielectric material during manufacture of a printed circuit board. The composition contains a corrosion inhibitor, an inorganic acid, and an alcohol which is effective to increase copper-loading in the composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/619,198, filed on Jul. 14, 2003, issued as U.S. Pat. No. 7,232,478 onJun. 19, 2007, which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

This invention relates to improving adhesion of metal surfaces, such ascopper to an insulating layer, in the manufacture of printed circuitboards.

A multilayer circuit board (MLB) has, among other things, a number ofmetal layers defining circuit patterns, and a number of insulatinglayers there-between. The metal layers defining circuit patterns todayare typically formed from copper, and the insulating layers aretypically formed from a resinous fiber-impregnated dielectric material.These respective layers can have a wide variety of thickness. Forexample, they can be on the order of only microns thick, or muchthicker.

In manufacturing MLBs, it is desirable to enhance the adhesion betweenthe conducting and insulating layers to avoid delamination in subsequentmanufacturing operations or in service. So called “black oxide”processes had been used for years which created a strongly adherentcopper oxide layer to which an insulating layer would adhere better.Black oxide processes have, for most of the industry, been replaced byprocesses such as described in U.S. Pat. No. 5,800,859 involvingformation of an organometallic conversion coating (OMCC). These OMCCprocesses involve exposing the copper circuit layer to an adhesionpromotion solution, which contains various components including anoxidizer, an inhibitor, and a mineral acid.

One limitation on OMCC processes has been that after processing a numberof boards through the same solution, sludge can form in the solution ascopper builds up. The effective life of a solution is therefore limitedby its tolerance for loading of copper. Another limitation is that theOMCC must be a uniform color, such as, for example, a dark brown orchocolate color. The industry associates this color with a uniformcoating which has strong adhesion properties. A dark uniform color ispreferred because it provides color contrast with copper to aid ininspection for defects. For example, it provides contrast for inspectionfor the so-called “pink-ring” defect. OMCC processes which producesignificantly lighter coatings are generally unacceptable, or at leastundesirable for most applications. For a lighter coating, “pink ring”defects are substantially more difficult to detect.

SUMMARY OF THE INVENTION

It is an aspect of this invention to provide an improved adhesionpromotion method and composition, one characterized by enhanced capacityfor copper loading, good peel strength, consistent and uniform OMCCcolor, resistance to thermal shock, and good adhesion between conductingand insulating layers.

Briefly, therefore, the invention is directed to an adhesion promotioncomposition for enhancing adhesion between a copper conducting layer anda dielectric material during manufacture of a printed circuit board, theadhesion promotion composition comprising a corrosion inhibitor, aninorganic acid, an oxidizing agent, and an alcohol which is effective toincrease copper-loading in the composition. The adhesion promotioncomposition is initially substantially free of transition metals havinga tendency to destabilize the oxidizing agent.

The invention is also directed to an adhesion promotion composition forenhancing adhesion between a copper conducting layer and a dielectricmaterial during manufacture of a printed circuit board, the adhesionpromotion composition comprising a corrosion inhibitor, an inorganicacid, an oxidizing agent, and an anionic surfactant. The adhesionpromotion composition is initially substantially free of transitionmetals having a tendency to destabilize the oxidizing agent.

In another aspect the invention is an adhesion promotion composition forenhancing adhesion between a copper conducting layer and a dielectricmaterial by formation of an organometallic conversion coating duringmanufacture of a printed circuit board. This adhesion promotioncomposition comprises a corrosion inhibitor, an inorganic acid, and anonionic surfactant, and the adhesion promotion composition is initiallysubstantially free of transition metals having a tendency to destabilizethe oxidizing agent.

The invention is also an adhesion promotion composition comprising acorrosion inhibitor, an inorganic acid, and a nonylphenolic nonionicsurfactant.

A further aspect of the invention is an adhesion promotion compositioncomprising a corrosion inhibitor, nitric acid, and an alcohol which iseffective to increase copper-loading in the composition.

Another aspect of the invention is a process for enhancing adhesionbetween a copper conducting layer and a dielectric material duringmanufacture of a printed circuit board, the process comprising exposingthe copper conducting layer to an adhesion promotion compositioncomprising a corrosion inhibitor, an inorganic acid, an oxidizing agent,and an alcohol which is effective to increase copper-loading in thecomposition, wherein the adhesion promotion composition is initiallysubstantially free of transition metals having a tendency to destabilizethe oxidizing agent, to thereby yield a microroughened copper surface.

Other aspects and features will be in part apparent and in part pointedout hereinafter.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

This invention includes an adhesion promotion composition, an adhesionpromotion composition concentrate, and a method for enhancing adhesion.The method can involve any dip, spray, or other process employed in theindustry for exposing a copper-conducting layer in a printed circuitboard manufacturing operation to an adhesion promoter. As a generalproposition, copper on the conducting layer is oxidized and some issolubilized. Cuprous copper generally dominates on the surface, andcupric copper generally dominates in solution. The cuprous copper on thesurface binds with the corrosion inhibitor to formcopper-inhibitor-complex as copper dissolves from the conducting copperlayer into the adhesion promoter chemistry at the same time. Thisresults in micro-roughened surface morphology of the conducting copperlayer. This micro-roughened copper surface promotes adhesion with thesubsequently applied insulating layer.

Hydrogen peroxide is incorporated into the adhesion promotioncomposition of the invention as an oxidizing agent to oxidize copper onthe substrate. Hydrogen peroxide is present in the adhesion promotioncomposition at a concentration of at least about 1 wt %. Theconcentration of hydrogen peroxide is typically no greater than about20%, and in certain preferred embodiments it is no greater than about10%. One most preferred concentration of hydrogen peroxide is from about0.5% by weight of the adhesion promotion composition to about 4% byweight. It has been found that when the concentration of hydrogenperoxide in the adhesion promotion composition is too high the structureof the roughened surface of the conducting layer forms a somewhatdendritic structure which is more fragile than the desired rougheningeffect, so that it forms a weaker bond than when lower concentrations ofhydrogen peroxide are used. Moreover, the OMCC becomes hazy if there isoveretching by too much hydrogen peroxide. All percentages herein are byweight unless indicated otherwise. Moreover, all concentrations arenormalized such that they refer to concentrations of each element as ifused in 100% concentrations. For example, in one embodiment the H₂O₂solution added to the composition is 35% concentrated H₂O₂, rather thana 100% concentrated H₂O₂. However, the 20%, 10%, 4% etc. numbersprovided above are % of 100% H₂O₂ in the final composition, not % of 35%H₂O₂ in the final composition.

To enhance the stability of the composition, the composition ispreferably initially substantially free of transition metals such ascopper which have a tendency to destabilize the oxidizing agent. Forexample, copper ions are avoided in the initial solution because theyhave a tendency to destabilize hydrogen peroxide. This requirementpertains to the initial composition in that the copper is avoided in thefresh composition before its use to promote adhesion. Upon use, however,copper is not excluded from the composition because, in fact, copperdoes tend to accumulate in the solution during use. The composition is“substantially” free of transition metals in that any trace amounts inthe composition are sufficiently low as to not significantly contributeto degradation of the oxidizing agent; for example, sufficiently low asto not increase the degradation rate by more than about 10%.

The adhesion promotion composition comprises one or more inorganic acidsfor the main purpose of solubilizing copper, and maintaining othercomponents of the composition in solution. A variety of acids, such asmineral acids including phosphoric acid, nitric acid, sulfuric acid, andmixtures thereof are workable. In one preferred embodiment both HNO₃ andH₂SO₄ are employed. It has been discovered that in addition tosolubilizing the Cu, H₂SO₄ helps to moderate the etch rate, andtherefore help prevent overetching of the substrate in isolated areas.The HNO₃ increases the etch rate; increases the solubility of Cu; helpsprevent premature sludge formation; and works synergistically with H₂O₂,H₂SO₄, and the corrosion inhibitor to darken the coating. The overallacid concentration in the composition is generally at least 1%,preferably at least 8%, and in certain preferred embodiments at least14% of the composition. The etch rate is slowed excessively if the acidconcentration is too high, with the exception of nitric acid, and canyield an organometallic conversion coating which is non-uniform and toolight in color. For this reason, the acidity level in previouscompositions had been typically selected to be about 20%. However, inthe present invention it is possible to push the acidity level up toabout 25% and above, because with the other additives described herein,the coating is not lightened as would otherwise be expected with an acidlevel elevated to about 25%. The overall acid level is typicallymaintained below about 50%. In one preferred embodiment, therefore,there is between about 22% and about 28% acid, including about 20% H₂SO₄(50% grade) and about 5% HNO₃ (95% grade) . In one preferred embodiment,the inorganic acid constitutes at least about 30% of the composition.Another preferred embodiment employs 28% H₂SO₄ (50% grade) and 5% HNO₃(95% grade). HNO₃ is employed in these preferred embodiments because ithas been discovered that it has a unique ability to solubilize theinhibitor-Cu complex better than do other mineral acids. While thesepercentages are percentages of the acids in the final composition andare based on use of 100% concentrated acid, as discussed above, thepreferred forms of the acids actually added are 50% concentrated H₂SO₄and about 95% concentrated HNO₃.

Inasmuch as certain of the preferred compositions employ HNO₃, theoverall composition is formulated to be compatible therewith. Inparticular, thiourea-based complexing agents are specifically avoideddue to the explosive nature thereof when mixed with HNO₃.

In general, triazoles, tetrazoles, imidazoles and mixtures thereof havebeen proposed as corrosion inhibitors in adhesion promotioncompositions. Benzotriazole (BTA) compounds are most preferred due totheir effectiveness in chelating Cu, their effectiveness to inhibitcorrosion, and their effectiveness to help darken the OMCC surface. Themost preferred BTA compound currently is 1,2,3-benzotriazole, also knownas aziamino-benzene or benzene azimide, and has the formula C₆H₄NHN₂.Particularly desirable results are achieved with corrosion inhibitorconcentrations of at least 0.1%, more preferably more than 0.5% byweight, and something more than 1% by weight. Generally, the corrosioninhibitor will be present in the composition in an amount no greaterthan 20%, preferably no greater than 10%, and more preferably less than5% by weight of the total weight of the adhesion promotion composition.High concentrations, such as more than 5% can be desirable as they canallow a reduction in the processing time. In certain preferredembodiments, however, the concentration is less than 5% or even lessthan 1%.

The invention also employs various additives to the adhesion promotingcomposition, as discussed in more detail below, selected from amongmonomeric and oligomeric alcohols, and polymeric, oligomeric, andmonomeric alcohol derivatives, including, but not limited to alcoholsulfates, sulfonates, and ethoxylates.

One embodiment of the invention employs a sulfonated anionic surfactant.It has been discovered that in addition to surface wetting, thissurfactant helps to stabilize the H₂O₂. The most particularly preferredof such surfactants is dodecylbenzene sulfonic acid (DDBSA). DDBSA isavailable from Ashland Distribution Company of Santa Ana, Calif.; orfrom Pilot Chemical Company of Santa Fe Springs, Calif. under the tradedesignation Calsoft LAS 99. Other such surfactants include sodiumdodecylbenzene sulfonate available from Witco Corporation, OrganicDivision, of New York, N.Y. under the trade designation Witconate 1850;isopropyl amine branched alkyl benzene sulfonate available from StepanCompany of Northfield, Ill. under the trade designation Polystep A-11;and TEA dodecylbenzene sulfonate available from Norman, Fox & Company ofVernon, Calif. under the trade designation Norfox T-60. This surfactantis used in a quantity sufficient to achieve surface wetting and H₂O₂stabilization, which quantity can vary depending on the overallcomposition of the adhesion promoter. One currently preferred embodimentincludes at least about 0.0001% of sulfonated anionic surfactant. As ageneral proposition, the sulfonated anionic surfactant concentration isat least about 0.005%, preferably at least about 0.1%; and is less thanabout 10%, preferably less than about 5%, more preferably less thanabout 2%. One specific example employs 0.002% of this surfactant,particularly DDBSA.

A currently preferred embodiment of the invention also incorporates asulfated anionic surfactant. One preferred example of this compound issodium 2-ethylhexyl sulfate, also known as 2-ethylhexanol sulfate sodiumsalt, having the formula C₄H₉CH(C₂H₅)CH₂SO₄Na. This is available fromNiacet Corporation of Niagara Falls, N.Y. under the trade designationNiaproof 08, which contains 38.5 to 40.5% sodium 2-ethylhexyl sulfateand the balance water. Alternatives include sodium tetradecyl sulfateavailable from Niacet under the trade designation Niaproof 4, sodiumlauryl sulfate available from Stepan Company of Northfield, Ill. underthe trade designation Polystep B-5, and sodium n-decyl sulfate availablefrom Henkel Corporation/Emery Group, Cospha/CD of Ambler, Pa. under thetrade designation Sulfotex 110. The addition of a sulfated anionicsurfactant compound surprisingly permits the acidity level to be raised,without the expected detrimental effect of lightening the coating.Because the acidity level can be raised in this manner, copper loadingis increased. It also helps darken the coating. This compound is presentin this embodiment in a concentration sufficient to increase copperloading without substantial lightening of the coating. The typicalconcentration is at least about 0.001%, and preferably at least about0.1%. The concentration of sulfated anionic surfactant is no greaterthan about 10%, and preferably no greater than about 5%. One preferredrange is between about 0.05 and 2%. In one preferred embodiment thesulfated anionic surfactant concentration is about 0.5%. In another itis 0.15%.

In a currently preferred embodiment, the composition also includes oneor more ethoxylated phenol derivatives as a nonionic surfactant. Thissurfactant has been discovered to provide the unexpected additionalbenefit of improving peel strength. In one preferred embodiment thissurfactant is one or more ethoxylated nonylphenols, such aspolyoxyethylene nonylphenol. Polyoxyethylene nonylphenol is availablefrom Dow Chemical Company of Midland, Mich. under the trade designationTergitol NP9. Alternatives include an ethoxylated nonylphenol availablefrom Dow Chemical Company of Midland, Mich. under the trade designationTergitol NP8, nonylphenoxypolyethoxyethanol available from Union CarbideCorporation of Danbury, Conn. under the trade designation Triton N, andethoxylated nonylphenol (or nonoxynol-2) available from Rhone-Poulenc,Surfactant & Specialty Division of New Jersey under the tradedesignation Igepal CO-210. The concentration of this surfactant isselected to be sufficient to improve peel strength. One currentlypreferred embodiment includes at least about 0.0001% of an ethoxylatedphenol derivative. As a general proposition, the concentration is atleast about 0.01%, preferably at least about 0.2%; and is less thanabout 10%, preferably less than about 5%. One preferred range is betweenabout 0.0001% and about 2%. One exemplary embodiment contains 0.02%.

It has been discovered that incorporating monohydric, dihydric,trihydric, primary, secondary, and/or tertiary alcohols that solubilizethe BTA copper complex can enhance copper loading of the adhesionpromotion composition. Suitable aliphatic saturated alcohols may be1,2-(ethylene glycol, propane-1,2-diol, butane-1,2-diol,etc.),1,3-(propane-1,3-diol, butane-1,3-diol, etc.),1,4-(butane-1,4-diol,hexane-1,4-diol, etc.), 1,5- ,etc. Then there areunsaturated diols, such as butene diol, hexene diol, and acetylenicssuch as butyne diol. An example of a suitable trihydric alcohol isglycerol. Alcohols among suitable monohydric, dihydric, and/or trihydricalcohols, are triethylene glycol, ethylene glycol, diethylene glycol,diethylene glycol methyl ether, triethylene glycol monomethyl ether,triethylene glycol dimethyl ether, propylene glycol, dipropylene glycol,glycerol(trihydric), tetrahydrofurfuryl alcohol, gamma-butyrolactone,1,4-butanediol, 2-butene-1,4-diol(unsaturated), 1,6-hexanediol,methanol, and isopropanol. This additive is present in this embodimentat a concentration sufficient to increase copper loading of thecomposition. Typically, this concentration is at least about 0.01%, andin certain embodiments is at least about 0.5%. The concentration of thisadditive is no greater than about 20%, and in certain embodiments nogreater than about 10%.

One preferred alcohol example that has proven to be especially effectiveis the oligomer triethylene glycol (TEG). In particular, compositionscontaining this oligomer have copper-loading capacity of about 30 gramscopper per liter solution up to about 35 and even about 40 g/L in dipprocess applications. In spray process and flooded immersion processapplications, automated and conveyorized applications, thesecompositions have copper-loading capacity of up to about 45 g/L and evenup to 50 g/L. This triethylene glycol is an oligomer in that it is amolecule of intermediate relative molecular mass with a structurecomprising a small number of units derived from molecules of lowerrelative molecular mass. This is in contrast to a polymer, which has ahigh relative molecular mass. This triethylene glycol is also oligomericin that its properties vary significantly with removal of one of itsunits; as opposed to polymeric compounds, with which removal of one or afew units has a relatively negligible effect on molecular properties.This triethylene glycol has the molecular formula C₆H₁₄O₄, morespecifically, HO(C₂H₄O)₃H, and a molecular weight of 150.17. Triethyleneglycol is present in this embodiment at a concentration of at leastabout 0.01%, typically at least about 0.5%, and in one embodiment atleast about 0.8%. The concentration of TEG is no greater than about 20%,and preferably no greater than about 10%. In a currently preferredembodiment the TEG concentration is about 1%. The TEG also has the addedbenefit of helping to stabilize the H₂O₂.

The composition optionally also includes an additional stabilizing agentfor the H₂O₂. Suitable stabilizing agents include, for example,dipicolinic acid, diglycolic and thiodiglycolic acid, ethylene diaminetetra-acetic acid and its derivatives, magnesium salt of anaminopolycarboxylic acid, sodium silicate, phosphates, phosphonates, andsulfonates. When the composition includes a stabilizing agent,preferably the stabilizing agent is present in an amount of from 0.001%or even at least 0.005% by weight of the adhesion promotion composition.Generally there is no more than 1% by weight in the composition. Thecurrently preferred composition contains an additional stabilizingagent, but relies primarily on the stabilizing function of the TEG, asdescribed above.

The composition further includes a source of halide ions. This source ispreferably HCl, and provides a chloride ion concentration in the rangeof about 10 to 100 ppm. The most preferred range for one embodiment isbetween about 60 and 65 ppm. Preferred ranges are different for otherembodiments depending on the overall composition and application. Thisincreased Cl⁻ level in comparison to previous formulations helps toincrease the ratio of cuprous copper to cupric copper, which has beendiscovered to increase peel strength. The Cl⁻ level tapers off and thenstabilizes during use of the composition. As such, an initial Cl⁻ ionconcentration of between about 20 ppm and about 100 ppm is preferred inone embodiment in order to achieve a Cl⁻ ion content in service of onthe order of about 20 to 80 ppm.

The adhesion promotion composition is manufactured by mixing thecomponents in an aqueous solution, preferably using deionized water. Inaccordance with standard safe practice, hydrogen peroxide is added tothe composition in a diluted form.

The copper surface is contacted with the adhesion promotion compositiongenerally without any pre-treatment. The copper surface may havepreviously been provided with a tarnish-inhibiting coating, e.g., byincorporating the tarnish inhibitor into a resist stripping compositionused in an immediately preceding step of etch resist stripping. Tarnishinhibitors used in such strippers are, for example, a triazole or othercoating. If so, it may be desirable to pre-clean the copper surface withan acidic pre-cleaner such as PC 7077 or PC 7086 or PC 7096 (trademarksfor products of Enthone Inc. of West Haven, Conn.), before contact withthe composition. Preferably prior to contact with the adhesion promotioncomposition, the copper surface will be substantially dry or have onlyminimal wetness. Apart from such a cleaning step, it is generallyunnecessary to carry out any pretreating steps. In a preferredembodiment of the invention, the adhesion promotion step followsimmediately after an etch resist stripping step or there is a singleprecleaning step between the etch resist stripping step and the adhesionpromotion step.

Contact with the adhesion promotion composition may be by anyconventional means, for example by immersion in a bath of the adhesionpromotion composition or by spraying or any other means of contact.Contact may be as part of a continuous process. As is well understood inthe art, immersion processes involve simply dipping the substrate into abath of the composition for the desired period. Spray processestypically involve application using a series of automated squeegee-typemechanisms. The method of application is not critical to the invention.However, as discussed above, the tolerance for copper loading can begreater for spray processes than for dip processes because, for example,there is more bath stagnation with dip processes.

Contact of the copper surface with the adhesion promotion composition istypically at a temperature between about 20 degree C. and about 40degree C., though temperatures reasonably outside this range areoperable. The contact time is generally no less than 1 second,preferably no less than 5 seconds, and often at least 10 seconds, mostpreferably at least 30 seconds. The maximum contact time may be up to 10minutes, although preferably the contact time is no greater than 5minutes, most preferably no greater than 2 minutes. A contact time ofabout 1 minute or less than 1 minute is standard. If the contact time ofthe adhesion promotion composition with the copper surface is too long,there is a risk that the copper surface may be etched away due todissolution and/or that a deposit other than the micro-porouscrystalline deposit that forms the micro-roughened surface will bedeposited onto the surface of the conducting material.

After contact of the copper surface with the adhesion promotioncomposition to form the microroughened surface, generally a pre-preglayer may be placed directly adjacent to the copper surface and thepre-preg layer adhered directly to the copper surface in the adhesionstep, forming a multi-layer PCB. Generally in the adhesion step heat andpressure are applied to initiate the adhesion reaction. In the adhesionstep, mechanical bonding is due to penetration of the polymeric materialof the insulating layer into the microroughened surface provided in theadhesion promotion step. Although it may be desirable to follow theadhesion promotion step with a specially formulated rinse step, it isoften adequate to rinse just with water.

A pre-preg insulating layer is applied directly to the microroughenedsurface, i.e., preferably without any intermediate metal deposition ontothe microroughened surface or the like, although optionally with apost-treatment cupric oxide removal or reduction operation to furtherenhance the bond strength as disclosed in U.S. Pat. No. 6,294,220.Pressure is applied by placing the layers that are to form themulti-layer laminate of the PCB in a press. Where pressure is applied itis generally from 100 to 400 psi, preferably from 150 to 300 psi. Thetemperature of this adhesion step will generally be at least about 100degree C., preferably between about 120 degree C. and about 200 degreeC. The adhesion step is generally carried out for any period from 5minutes to 3 hours, most usually from 20 minutes to 1 hour, but is forsufficient time and pressure and at a sufficiently high temperature toensure good adhesion between the first and second layers. During thisadhesion step, the polymeric material of the insulating layers,generally an epoxy resin, tends to flow ensuring that the conductivepattern in the metal is substantially sealed between insulating layers,so subsequent penetration of water and air is avoided. Several layersmay be placed together in the adhesion step to effect lamination ofseveral layers in a single step to form the MLB.

Though the exemplary arrangement discussed at length herein is apre-preg layer adhered to a copper surface, the invention also includesimproving adhesion of other dielectric materials, whether permanent ortemporary, to copper. For example, the invention improves adhesionbetween copper and a solder mask that is dielectric. It similarlyimproves copper adhesion with inks, polymeric photo-resists, and dryfilms. It also has application in connection with photoimageabledielectrics or other dielectrics used in the context of high densityinterconnect and sequential build up technologies.

In one form the invention is a ready-to-use adhesion promotioncomposition that can be used directly for immersion or other exposure ofthe substrate. In another form the invention is a concentrate that is tobe diluted to form the composition for immersion or other exposure.

An exemplary ready-to-use composition includes the following:

-   -   0.5 to 8 wt % H₂O₂    -   16 to 25 wt % H₂SO₄    -   0.1 to 10 wt % HNO₃    -   0.1 to 2 wt % 1,2,3-benzotriazole    -   0.01 to 5 wt % triethylene glycol    -   0.05 to 2 wt % 2-ethyloxosulfonate (Niaproof 08)    -   0.0001 to 2 wt % dodecylbenzene sulfonic acid (DDBSA)    -   0.0001 to 2 wt % polyoxyethylene nonylphenol (Tergitol NP9)    -   40 to 70 wt % deionized water

When provided as a concentrate, the ranges described above for thepreferred proportions of the ingredients are essentially doubled,because the product is diluted with, for example, 50% water uponformulation of the composition for use. In one embodiment, theconcentrate has the following ingredients:

-   -   32-50 wt % H₂SO₄    -   0.2 to 20 wt % HNO₃    -   0.2 to 4 wt % 1,2,3-benzotriazole    -   0.02 to 10 wt % triethylene glycol    -   0.002 to 4 wt % 2-ethyloxosulfonate (Niaproof 08)    -   0.0002 to 4wt % dodecylbenzene sulfonic acid (DDBSA)    -   0.0002 to 4 wt % polyoxyethylene nonylphenol (Tergitol NP9)

The H₂O₂ is added later and is not included in the concentrateformulation. This concentrate is then incorporated into an overallsolution in which, for example, about 43 wt % is this concentrate, about7 wt % is H₂O₂, and about 50 wt % is water.

EXAMPLE 1

Five sample adhesion promotion compositions A through E were prepared bymixing the components in the percentages in Table 1 to form aqueouscompositions. TABLE 1 Example Example Example Example Example RawMaterial A B C D E H₂O₂ 7.2 7.2 7.2 7.2 7.2 H₂SO₄ 28.0 28.0 28.0 28.028.0 HNO₃ 5.0 5.0 5.0 5.0 5.0 1,2,3-Benzotriazole 1.0 1.0 1.0 1.0 1.0Triethylene glycol 0.00 0.00 0.00 0.00 0.9 2-ethyoxosulfonate 0.00 0.000.00 0.15 0.15 (Niaproof 08) Dodecylbenzene 0.00 0.002 0.002 0.002 0.002Sulfonic acid (DDBSA) Polyoxyethylene 0.00 0.00 0.002 0.002 0.002Nonylphenol (Tergitol NP 9) Water (Deionized) 58.8 58.8 58.79 58.6557.75 Peel Strength 5.58 N/A 6.32 N/A 7.0 (lb./inch) Coating Appearance2 3 4 5 5 Rating* Sludge (After 120 10 N/A N/A 6 0.001 hrs @ 40-50 g/lof Cu++ loading (% by volume) Organic Inhibitor % 3.4 2.29 N/A 1.6 N/ADrop Chloride Stability 2.2 3.25 N/A 2.4 N/A (Drop in ppm) HydrogenPeroxide: 0.174 0.112 N/A 0.117 N/A vol. % DropNote:a) Wt % Based on 100% of Examples &b) N/A = Test was either not conducted or not available.Key to Coating Appearance Rating5 = Uniform dark reddish brown4 = Fairly uniform dark reddish brown3 = Fairly uniform reddish brown2 = Not uniform, light reddish brown

Copper foil samples (Samples A through E) of the dimensions 5 in×5 in×1mil (12.7 cm×12.7 cm×25 microns) were treated with the compositions Athrough E, respectively, by immersion for about 45 to 60 seconds to forman organometallic conversion coating. The substrates were then rinsedand dried.

EXAMPLE 2

Samples A, C, and E were bonded to a 370 FRA pre-preg material bypressing and baking. Lithographers' tape #616 available from 3M Companyof St. Paul, Minn. was adhered to the copper side of the sample. Thedimensions of each piece of tape were about ⅛ inch×5 inches (0.3 cm×12.7cm). The tape was then pulled to separate the copper foil from theprepreg by use of a Peel Strength Tester (Model TA620-30) available fromCECO of Garden Grove, Calif.. The peel strengths of samples A, C, and Ewere 5.58, 6.32, and 7.0 lbs/inch, (991, 1131, and 1253 gms/cm),respectively. These results reveal that the adhesion promoter employingan oligomeric alcohol (triethylene glycol), the sulfated anionicsurfactant (Niaproof 08), and the sulfonated anionic surfactant (DDBSA)provided the best adhesion.

EXAMPLE 3

The samples were visually inspected for coating appearance and ranked ona scale of 1 to 5 of increasing darkness and uniformity, with 5corresponding to uniform dark reddish brown, 4 corresponding to fairlyuniform dark reddish brown, 3 corresponding to fairly uniform reddishbrown, and 2 corresponding to non-uniform light reddish brown. Thecoating appearances were graded as shown in Table 1, revealing that thebest coating appearances were obtained with compositions D and E.

EXAMPLE 4

Compositions A, D, and E were tested for the formation of sludge byadding 40-50 g/L Cu++ and allowing them to stand at ambient conditionsfor 120 hours. The volume of sludge formed as a percentage of theoverall volume of the solutions is presented in Table 1. These resultsreveal that the inclusion of the oligomeric alcohol (triethylene glycol)has a substantial positive impact on copper loading. In particular, lessthan about 0.1 volume % of Cu-containing sludge is formed at 120 hoursunder ambient conditions when the composition is loaded with between 40and 50 g/liter Cu ions.

EXAMPLE 5

Samples A, B, and D, were tested for stability of organic inhibitor1,2,3-benzotriazole (BTA). UV Vis Spectrophotometer analysis revealedthe % drops in organic inhibitor after about 120 hours presented inTable 1. The more stable performance was achieved with composition D.

EXAMPLE 6

Samples A, B, and D, were tested for chloride stability by volumetrictitration. The ppm drop in chloride ion concentration after 120 hours ispresented in Table 1. The performances were comparable to each other,illustrating that the additives of the invention do not negativelyaffect chloride stability.

EXAMPLE 7

Samples A, B, and D, were tested for hydrogen peroxide stability byvolumetric titration. The % drops in hydrogen peroxide concentrationafter 120 hours is presented in Table 1. The performances werecomparable to each other, illustrating that the additives of theinvention do not negatively affect hydrogen peroxide stability.

When introducing elements of the present invention or the preferredembodiment(s) thereof, the articles “a,” “an,” “the,” and “said” areintended to mean that there are one or more of the elements. The terms“comprising,” “including,” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

The foregoing relates to a limited number of embodiments that have beenprovided for illustration purposes only. It is intended that the scopeof invention is defined by the appended claims and there aremodifications of the above embodiments that do not depart from the scopeof the invention.

1. An adhesion promotion composition for enhancing adhesion between acopper conducting layer and a dielectric material during manufacture ofa printed circuit board, the adhesion promotion composition comprising acorrosion inhibitor, an inorganic acid, an oxidizing agent, and anoligomeric, polyhydric alcohol which is effective to increasecopper-loading in the composition, wherein the adhesion promotioncomposition is initially substantially free of transition metals havinga tendency to destabilize the oxidizing agent.
 2. The adhesion promotioncomposition of claim 1 wherein the alcohol is selected from amongoligomeric, dihydric alcohols.
 3. The adhesion promotion composition ofclaim 1 wherein the alcohol is selected from among oligomeric dihydricalcohols and constitutes between about 0.5 wt % and about 20 wt % of thecomposition.
 4. The adhesion promotion composition of claim 1 whereinthe alcohol is selected from among oligomeric, trihydric alcohols. 5.The adhesion promotion composition of claim 1 wherein the alcohol isselected from among oligomeric trihydric alcohols and constitutesbetween about 0.5 wt % and about 20 wt % of the composition.
 6. Theadhesion promotion composition of claim 1 wherein the alcohol istriethylene glycol.
 7. The adhesion promotion composition of claim 1wherein the alcohol is triethylene glycol and constitutes between about0.5 wt % and about 20 wt % of the composition.
 8. The adhesion promotioncomposition of claim 1 wherein the composition has a copper-loadingcapacity of at least about 30 grams copper per liter composition.
 9. Theadhesion promotion composition of claim 1 wherein less than about 0.1volume % of Cu-containing sludge is formed at 120 hours under ambientconditions when the composition is loaded with between 40 and 50 g/literCu ions.
 10. The adhesion promotion composition of claim 1 furthercomprising an anionic surfactant.
 11. The adhesion promotion compositionof claim 1 further comprising an anionic surfactant selected from amongpolymeric, oligomeric, and monomeric alcohol derivatives.
 12. Theadhesion promotion composition of claim 1 further comprising an anionicsurfactant selected from among alcohol sulfates, sulfonates, andethoxylates.
 13. The adhesion promotion composition of claim 1 furthercomprising dodecylbenzene sulfonic acid (DDBSA) as an anionicsurfactant.
 14. The adhesion promotion composition of claim 1 furthercomprising a nonionic surfactant.
 15. The adhesion promotion compositionof claim 14 wherein the nonionic surfactant is an ethoxylated alcoholderivative.
 16. The adhesion promotion composition of claim 15 whereinthe nonionic surfactant is polyoxyethylene nonylphenol.
 17. The adhesionpromotion composition of claim 1 wherein the inorganic acid constitutesat least about 30 wt % of the composition.
 18. The adhesion promotioncomposition of claim 1 wherein the inorganic acid is a mixture ofsulfuric acid and nitric acid and constitutes at least about 30 wt % ofthe composition.
 19. An adhesion promotion composition for enhancingadhesion between a copper conducting layer and a dielectric materialduring manufacture of a printed circuit board, the adhesion promotioncomposition comprising a corrosion inhibitor, an inorganic acid, anoxidizing agent, an alcohol which is effective to increasecopper-loading in the composition wherein the alcohol is dihydric ortrihydric, and an anionic surfactant, wherein the adhesion promotioncomposition is initially substantially free of transition metals havinga tendency to destabilize the oxidizing agent.
 20. The adhesionpromotion composition of claim 19 wherein the alcohol is selected fromamong dihydric alcohols.
 21. The adhesion promotion composition of claim19 wherein the alcohol is selected from among dihydric alcohols andconstitutes between about 0.5 wt % and about 20 wt % of the composition.22. The adhesion promotion composition of claim 19 wherein the alcoholis triethylene glycol.
 23. The adhesion promotion composition of claim19 wherein the alcohol is triethylene glycol and constitutes betweenabout 0.5 wt % and about 20 wt % of the composition.
 24. The adhesionpromotion composition of claim 19 wherein the alcohol is selected fromamong trihydric alcohols.
 25. The adhesion promotion composition ofclaim 19 wherein the alcohol is selected from among trihydric alcoholsand constitutes between about 0.5 wt % and about 20 wt % of thecomposition.
 26. The adhesion promotion composition of claim 19 whereinthe composition has a copper-loading capacity of at least about 30 gramscopper per liter composition.
 27. The adhesion promotion composition ofclaim 19 wherein less than about 0.1 volume % of Cu-containing sludge isformed at 120 hours under ambient conditions when the composition isloaded with between 40 and 50 g/liter Cu ions.
 28. The adhesionpromotion composition of claim 19 further comprising an anionicsurfactant.
 29. The adhesion promotion composition of claim 19 furthercomprising an anionic surfactant selected from among polymeric,oligomeric, and monomeric alcohol derivatives.
 30. The adhesionpromotion composition of claim 19 further comprising an anionicsurfactant selected from among alcohol sulfates, sulfonates, andethoxylates.
 31. The adhesion promotion composition of claim 19 furthercomprising dodecylbenzene sulfonic acid (DDBSA) as an anionicsurfactant.
 32. The adhesion promotion composition of claim 19 furthercomprising a nonionic surfactant.
 33. The adhesion promotion compositionof claim 32 wherein the nonionic surfactant is an ethoxylated alcoholderivative.
 34. The adhesion promotion composition of claim 33 whereinthe nonionic surfactant is polyoxyethylene nonylphenol.
 35. The adhesionpromotion composition of claim 19 wherein the inorganic acid constitutesat least about 30 wt % of the composition.
 36. The adhesion promotioncomposition of claim 19 wherein the inorganic acid is a mixture ofsulfuric acid and nitric acid and constitutes at least about 30 wt % ofthe composition.
 37. An adhesion promotion composition for enhancingadhesion between a copper conducting layer and a dielectric materialduring manufacture of a printed circuit board, the adhesion promotioncomposition comprising a corrosion inhibitor, an inorganic acid, anoxidizing agent, and an oligomeric, polyhydric alcohol which iseffective to increase copper-loading in the composition, wherein theinorganic acid is a mixture of sulfuric acid and nitric acid andconstitutes between about 22 and about 28 wt % of the composition. 38.An adhesion promotion composition for enhancing adhesion between acopper conducting layer and a dielectric material during manufacture ofa printed circuit board, the adhesion promotion composition comprising acorrosion inhibitor, an inorganic acid, an oxidizing agent, and anoligomeric, polyhydric alcohol which is effective to increasecopper-loading in the composition, wherein the inorganic acid is amixture of sulfuric acid and nitric acid and constitutes at least about30 wt % of the composition.